How to Offline Sign Transactions using C# for TRON blockchain?

using Google.Protobuf;
using Protocol;
using System;
using System.Net;
using System.Security.Cryptography;
using Org.BouncyCastle.Asn1.Sec;
using Org.BouncyCastle.Asn1.X9;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Security;
 
public class OfflineSigner
{
    public void SignAndSendTransaction()
    {
        // Define transaction
        TransferContract contract = new TransferContract()
        {
            OwnerAddress = ByteString.CopyFrom(DecodeFromBase58Check("Sender Address")),
            ToAddress = ByteString.CopyFrom(DecodeFromBase58Check("Receiver Address")),
            Amount = 10 // Amount of TRX to send
        };
 
        // Create transaction
        Transaction transaction = new Transaction()
        {
            RawData = new Transaction.Types.raw()
            {
                Contract = { new Transaction.Types.Contract()
                {
                    Type = Transaction.Types.Contract.Types.ContractType.TransferContract,
                    Parameter = Any.Pack(contract)
                }},
                Timestamp = Convert.ToInt64((DateTime.UtcNow - new DateTime(1970, 1, 1)).TotalMilliseconds),
                Expiration = Convert.ToInt64((DateTime.UtcNow.AddHours(1) - new DateTime(1970, 1, 1)).TotalMilliseconds)
            }
        };
 
        // Sign transaction
        transaction.Signature.Add(ByteString.CopyFrom(SignTransaction2Byte(transaction, "Your private key")));
 
        // Serialize transaction to bytes
        byte[] transactionBytes = transaction.ToByteArray();
 
        // When you're online, send the transaction over to the TRON network
        // WebRequest or HttpClient can be used here to post the transactionBytes to the network
    }
 
    private byte[] SignTransaction2Byte(Transaction transaction, string priKey)
    {
        SHA256 sha256 = SHA256.Create();
        byte[] hash = sha256.ComputeHash(transaction.RawData.ToByteArray());
 
        X9ECParameters ecParams = SecNamedCurves.GetByName("secp256k1");
        ECDomainParameters domainParams = new ECDomainParameters(ecParams.Curve, ecParams.G, ecParams.N, ecParams.H, ecParams.GetSeed());
        ECPrivateKeyParameters privateKeyParameters = new ECPrivateKeyParameters(new BigInteger(priKey, 16), domainParams);
        ECDsaSigner signer = new ECDsaSigner();
        signer.Init(true, privateKeyParameters);
 
        BigInteger[] sigs = signer.GenerateSignature(hash);
        byte[] sigBytes = new byte[64];
        byte[] r = sigs[0].ToByteArray();
        byte[] s = sigs[1].ToByteArray();
 
        Array.Copy(r, 0, sigBytes, 32 - r.Length, r.Length);
        Array.Copy(s, 0, sigBytes, 64 - s.Length, s.Length);
 
        return sigBytes;
    }
 
    // Method to decode address from Base58Check
    private byte[] DecodeFromBase58Check(string address)
    {
        // Implementation goes here. You might need to use an external library or implement the decoding process yourself.
    }
}